[heap] Decouple SpaceIterator from ObjectIterator.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 2248 matching lines @@
 
  private:
   ObjectStatsCollector live_collector_;
   ObjectStatsCollector dead_collector_;
 };
 
 void MarkCompactCollector::VisitAllObjects(HeapObjectVisitor* visitor) {
   SpaceIterator space_it(heap());
   HeapObject* obj = nullptr;
   while (space_it.has_next()) {
-    ObjectIterator* it = space_it.next();
-    while ((obj = it->Next()) != nullptr) {
+    std::unique_ptr<ObjectIterator> it(space_it.next()->GetObjectIterator());
+    ObjectIterator* obj_it = it.get();
+    while ((obj = obj_it->Next()) != nullptr) {
       visitor->Visit(obj);
     }
   }
 }
 
 void MarkCompactCollector::RecordObjectStats() {
   if (FLAG_track_gc_object_stats) {
     ObjectStatsVisitor visitor(heap(), heap()->live_object_stats_,
                                heap()->dead_object_stats_);
     VisitAllObjects(&visitor);
@@ skipping 1761 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8